1. Field of the Invention
This invention generally relates to packaging and more specifically to a storage bag that is easily reclosed and opened and to the methods and apparatus for making such a storage bag.
2. Description of Related Art
There is a long-running effort to make a storage bag that is easily opened and then reclosed. This effort has led to criteria for judging the potential success of such storage bags. Consumers require that such bags must be easily opened, reclosed, and then reopened. The method of reclosure must be positive. From a manufacturer's standpoint, the method and apparatus required for forming the bag and reclosure structure must be easily added to a production line, operate without any appreciable reduction in production rates, add minimal production costs, have the capacity to be used with bags requiring a freshness seal and produce little or no waste material. Generally this prior effort has produced bags that either incorporate a separate reclosable tie or an integral structure that forms a tie.
The following patents are examples of bags with separate reclosure ties:
______________________________________ 3,311,288 (1967) Lemelson 3,426,959 (1969) Lemelson 3,674,135 (1972) Simon 3,779,139 (1973) White ______________________________________
Each Lemelson patent discloses packages with a tear strip of plastic or metallic foil. The tear strip may include a thread, string, wire or weld for added strength. The bag is reclosed by separating the tie from the bag and then wrapping and twisting the tie around the bag.
The Simon patent discloses a roll of separable bags. A line of perforations along an edge or top of each bag enables a section of the material to be removed for use as a reclosure tie or tear strip. The tear strip may be reinforced by one or more heat seals or by the application of separate strengthening materials such as string, deformable metal or another ply of film.
The White patent discloses a bag with a transverse tear strip that can be removed from the end of the bag. This tear strip then can be tied in an overhand knot to reclose the bag.
Each of the foregoing reclosure tie structures achieve some of the previously discussed criteria. Most are relatively easy to use in reclosing a bag. Twisted tie wraps are also relatively easy to remove in order to reopen the bag. Those tied with overhand knots may or may not be easy to open depending upon the ease with which the overhand knot releases. However, these approaches have not found great acceptance because they all incorporate special structures or require very specialized apparatus that can reduce production rates or increase materials and manufacturing costs unacceptably. For example, the White patent discloses the formation of a bag with a series of steps that is not readily adapted to continuous form and fill processes as conventionally used in the food industry and other industries. It requires special apparatus.
The following patents disclose packaging that uses integral tie strips that remain attached to a bag:
______________________________________ 3,217,971 (1965) Shvetz 1,150,037 (1969) Plusplan (GB) 3,480,198 (1969) Repko ______________________________________
The Shvetz patent discloses a bag that opens along a transverse tear line that terminates inwardly of the edges of the bag to form a tie. A longitudinal tear line allows a portion of a reclosable tie to be separated into two halves such that the reclosure tie or strip forms two individual tie strips attached to opposite edges of the bag. The two ties can be knotted together. In another version a side strip formed along an edge of the bag can be partially separated to form a single tie strip.
The Plusplan patent discloses a similar structure in which a marginal section of a bag separates from the main portion of the bag along a tear line. However, the reclosure tie does not completely separate from the bag.
The Repko patent discloses a similar structure in which a marginal portion, with a weld or heat seal for strength, partly separates from a bag along a tear line defined by a series of apertures. The tear terminates at an end point, so the marginal portion remains physically attached to the bag.
Each of these structures either requires additional materials or prevents the bag from opening fully when the contents are to be dispensed. Moreover, the Repko patent requires a sophisticated structure for forming the plurality of apertures with seals intermediate and about each aperture to maintain any freshness seal.
The following patents disclose the bags in which a reclosure tie has an integral loop and tail section:
______________________________________ 3,664,575 (1972) Lake 4,549,657 (1985) Martin 4,609,107 (1986) Martin et al 4,682,976 (1987) Martin et al 4,787,517 (1988) Martin ______________________________________
In accordance with the Lake patent a portion of a bag adjacent the top is formed with an intermediate seal that extends partially across the bag to form a tail of a reclosure tie. Another transverse seal spaced from the first seal joins the layers of film to form a loop section. This reclosure tie can be separated from the bag and then cinches the bag when the tail is wrapped around the bag and thread through the loop. However this reclosure tie is disclosed in connection with storage bags without freshness seals. That adaptation of this structure to a bag with a freshness seal could increase material costs unacceptably.
The Martin patents, U.S. Pat. Nos. 4,549,657 and 4,787,517, disclose a number of embodiments of easily opened and reclosable bags. Oppositely disposed sealing jaws form a closure seal with a reclosure tie and a freshness seal. The reclosure tie can be removed from the bag without disturbing the freshness seal. The bag is reclosed by wrapping the reclosure tie around the bag and extending one end through a loop formed at the intermediate section by the unsealed plies. In one embodiment it is suggested that the reclosure tie be formed as sealed plies of material except at an intermediate section offset to one end of the tie, thereby to form a tail.
In each of the Lake and Martin patents the loop section incorporates a seal. In many applications, particularly those involving polyethylene-based film bags, this seal is subject to failure. More particularly, as a cinching force is applied by the tail portion, a large portion of that force concentrates at an edge of the seal in the loop section. The seal then can begin to fail due to delamination of the plies and tearing of the material. When this occurs, the integrity of the loop section is lost and the reclosure tie no longer is functional.
The Martin et al patents, U.S. Pat. Nos. 4,609,107 and 4,682,976, disclose a reclosure tie formed as a tear strip across a top of a polypropylene bag in a margin portion beyond a freshness seal. The tear strip has a mold formed transversely in the bag for strength; it tears along a series of specially formed slots or perforations through the material in the margin portion beyond the freshness seal. In one embodiment a portion of the bag omits the mold proximate an edge thereby to provide a reclosure tie with a short mold channel and a loop spaced from one end. It is suggested that the other end of the reclosure tie pass through the loop as a tail to cinch the bag. Cinching, in this case, is also dependent upon an interaction of nubs formed on the edges of the reclosure tie. This approach is disclosed in connection with heat sealable, treated cellophane or other thin organic polymer materials. In fact, the bag has been used with polypropylene bags, but is not readily adapted for polyethylene-based bags. First, it is difficult to form a mold and channel in such material. Second, the cinching forces still act against a seal thereby incorporating a potential failure point.